Ball mill for treating used casting sand

ABSTRACT

A ball mill for treating and washing used casting sand has a drum that includes an interior and exterior wall. The space between these interior and exterior walls form an intermediate chamber. Disposed along the exterior wall is a screen through which passes the treated sand. The drum may be positioned on an inclination with repect to the horizontal and has contained within its interior a plurality of mill balls. Feeding means are placed at, and comprise one end of the drum. The feeding means are placed so as to be concentric about the central longitudinal axis of the drum. Means are placed within the intermediate chamber to subdivide it into compartments. A continuously operating discharge means is disposed at, and comprises the other end of the drum so that the metallic residue of the casting sand migrates towards the discharge means and exits thereat as the drum revolves.

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States ate 1 1 Muller 1 1 Jan. 28, 1975 [541 BALL MILL FOR TREATWG USEDFOREIGN PATENTS OR APPLICATIONS CASTING SAND 190,283 5/1906 Germany241/74 [76] inventor: Karl A. Muller, Ruebcnacher Str. 542.323 6/1957Canada 209/291 89, 54 Kohlenz-Metternich, Germany Primary ExaminerRoyLake Assistant Emminer-E. F. Desmond 22 F1 d: M 3, 1973 i 1 le ayAttorney, Agent. or Firm-Allison C. Collard [2]] Appl. No.: 356,984

[57] ABSTRACT [30] Foreign Application Priority Dam A ball mill fortreating and washing used casting sand June 15, 1972 Germany 2229088 hasa drum that includes an interior and exterior wall, July 11, 1972Germany 2233923 The space between these interior and exterior walls forman intermediate chamber. Disposed along the ex- Cl l/ 8 terior wall is ascreen through which passes the treated l0 sand. The drum may bepositioned on an inclination [51] Int. Cl. 1302c 17/06, B07b 1/24 withrepect to the horizontal and has contained within Field of Search itsinterior a plurality of mill balls. Feeding means are L placed at, andcomprise one end of the drum. The 164/5 feeding means are placed so asto be concentric about the central longitudinal axis of the drum. Meansare [56] References Cited placed within the intermediate chamber tosubdivide it UNlTED STATES PATENTS into compartments. A continuouslyoperating dis- 594422 11/1897 Paul 241/179 X charge'means is dispmd atand comprise? the 242,423 10/1917 Cover-m 24m79X end of the drum so thatthe metallic residue of the 2,743,060 4/1956 Daman 241/183 casting Sandmigrates towards the discharge means 3,180,581 4/1965 Velcheff 241/171 Xand exits thereat as the drum revolves. 3,545,687 12/1970 Mosby 241/172x R12,778 4/190s- Bonvillain .1 241 /172 7 Clam, 6 D'awmg F'gures l1? I/3 2 l M E I 21 Q 6 a 3 8 H i g Q ,7 I8 T f'g I \g 7 i &

I 12 I5 4 I0 (1 la BALL MILL FOR TREATING USED CASTING SAND Thisinvention relates to a ball mill for treating or washing used castingsand. The ball mill essentially consists of a drum containing millballs, whereby the jacket or casing of the drum has a double wall and isformed like a screen (sieve), and a feeding means for the material inthe height of the drum axis.

Such devices treat or wash sand from foundries. separate core pins, aswell as metal pieces from the sand. As is known, the sand molds whichare used in foundries cannot be used again after the mold or cast isfinished. The sand molds are merely remotely stored. However, valuablematerial is lost because these sand molds contain metal pieces anduseable core sand.

It has been suggested to treat the used cores in a wet washing treatmentin order to retrieve the core sand. However, the suggested methods havefailed because of the size of the installation required and the highcosts involved.

Another device is known from US. Pat. No. 2,835,941 which crushes theagglomerate core sand by means of large balls. These balls are containedin a double walled rotating drum, whereby the face of the jacket orcasing is provided with slots and partly with screens or sieves. Whilethe sand drops into a container, the remaining core pins and residue aresepa' rately discharged at the periodic return movement of the drum.However, a disadvantage of this device is that it does not operatecontinuously, but must be interrupted periodically in order to dischargethe residue.

A mold sand treatment or washing installation is known from German Pat.No. 425,713. In this disclosure screen or sieve drums are concentricallydisposed one about the other. The screen drums are surrounded by ajacket or casing. These drums are formed in a polygon-like manner andare mounted eccentrically on a rotating shaft. The shaft rotatescounterclock-wise with respect to the rotation of the jacket. On theouter circumference of the outer screen, oblique transport shovels,paddles and kneading means are provided. A ball mill having a screentype jacket is provided in the end of the inner screen drum and islarger in its diameter. However, this device is not really a ball millin the conventional sense, but a device in which different operatingsteps for making mold sand are combined. The ball mill itself is in theshape of a cylinder and the balls are in the inside of the cylinder.This device does not permit a continuous mode of operation.

And, a mixing drum for sand treatment is known from German Petty Pat.No. 1,905,629. This patent teaches the use of a cylindrical body whereinheavy ball-like mill bodies are provided. The sand is fed into thedevice on one side together with the desired binder and drops through ascreen on the opposite end. In this drum only sand, already milled, canbe used and it must be separated from all residue. In order to pick upagglomerates, while simultaneously obtaining an even coating of thegranules by the binder, this device merely crushes or kneads the sand inany suitable manner.

The present invention overcomes the disadvantages of the aforementioneddevices by discharging the residue or remains in a continuous manner.This is achieved by utilizing a drum jacket or casing having aninclination with respect to the horizontal. The apparatus includesintermediate chambers which are longitudinally or axially subdivided. Acontinuously operating ring-like discharge opening for the noncrushableresidue is provided opposite the feeding portion of the drum.

The ball mill according to the present invention is furthercharacterized in that a hollow cylinder is provided as the dischargemeans for the residue.

In another embodiment of the inventive ball mill, the drum may beprovided with its jacket or casing face disposed horizontally. Inaddition, the apparatus places a plurality of rings between the innerbars of the drum and the outer screen or sieve thus subdividing the drumintermediate screen chamber into a plurality of sections. A returntransport bar is mounted for each section.

In the subject disclosure the material is fed through a hollow drumshaft. Guiding pieces are mounted on the inner bars of the drum. Adouble walled drum, partly containing a defined size of balls is chargedat the feed opening through a funnel and hollow shaft. The drum ismounted with an inclination descending toward the discharge opening. Aplate is provided at the front face of the discharge opening, leaving aring- ]ike opening between the inner walls of the drum and the edge ofthe plate. This ring-like opening is such that balls cannot passthrough. Consequently, the drum has a drum end section or zone intowhich the'residue and the core pins of the sand may enter, but in whichno balls are present. In this end section or zone the jacket face hasopenings so that the residue falls out radially. This is particularlyadvantageous for the adjacent drive. The drum is subdivided into anumber of sections, which reach to the end section of the drum, by aplurality of outer rings arranged over the inner jacket bars. Above thisa screen'jacket is mounted having defined screen mesh sizes. Sand andresidue up to a defined size can fall through the slots of the innerjacket. Sand which is smaller in diameter than the mesh size of thescreen falls through the screen for recycling. Larger parts are thrownback into the inner chamber of the drum through an opening at eachrotation of the drum. The balls again crush these parts which thentravel along the descending incline towards the discharge opening. Owingto repeated screening in the radial sections, increasing amounts of sandare screened out. Eventually the residue arrives at the last drumsection or zone where they are discharged. Accordingly, sand clumps willbe completely crushed and the metal parts will be freed from sand. Thus,continuous and economical sand recycling is assured. Owing to a linkdust removal installation, the sand may be removed for immediate use.

For material having a relatively high temperature the drum may bemounted on rollers. The rollers of the bearing at the discharge openingare supported by an axial pressure bearing. However, the rollers at thecharge openings are not provided with axial pressure bearings. This typeof bearing can be adjusted to the desired requirements.

In another embodiment of the invention the drum is mounted horizontallyand the guide sheet metal is mounted on the inner wall bars, for guidingthe material in the direction of the drum end section (zone). This sheetmetal is mounted helically on these inner wall bars.

In a further embodiment of the inventive ball mill, the inner wall barsin the end section of the drum have openings. These are sized so thatthe residue will be discharged but not the mill balls. In thisembodiment, material is fed through a hopper and a hollow shaft into theinner drum chamber. The inner drum chamber is mounted without an inclinebut has a double wall and is cylindrical and partly filled with balls.

The material is crushed by the balls until it falls through the slots ofthe inner screen jacket upon reach ing the proper mesh size. Or, thematerial is transported by the sheet metal guides in the direction ofthe drum end section. In this end section an additional section or zoneis provided having no outer screen, but has openings through which theresidue may fall. The openings are of smaller size to block the balls.Consequently, sand is screened out of the material and the residue isdischarged at the end of the drum. Mounting the drum horizontally avoidsspecial incline mounts for its support bearings. Construction andassembly of the drum according to the invention is substantiallyfacilitated.

It is therefore an object of the present invention to provide anapparatus for treating sand molds used in sand castings.

It is another object of the present invention to provide an apparatusfor continually discharging the separated materials and to provide anapparatus that is efficient in operation and simple in design.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings which disclose the embodiments of theinvention. It is to be understood, however, that the drawings aredesigned for the purpose of illustration only and not as a definition ofthe limits of the invention.

In the drawings wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 is a broken side view of the inventive apparatus;

FIG. 2 is a sectional view of the device of FIG. I taken on the line IIof FIG. 1 through the last chamber from the discharge opening to thecharge opening;

FIG. 3 is a roller bearing in a side view;

FIG. 4 is a simplified roller bearing in a front view;

FIG. 5 is a broken side view of another embodiment of the inventionhaving a horizontally mounted drum; and

FIG. 6 is the device taken along section A-B of FIG. 5.

Referring now to FIGS. 1 and 2, a drive 1, shown in part, revolves thedrum in direction D. The outer periphery of the drum forms a screencasing 2 which encompasses drum rings 3 up to a discharge chamber 8. Aninner casing comprises inner bars 13 and the return guide bars 15. Theseare mounted within drum rings 3 as shown. Discharge chamber 8 does nothave a screen drum and also lacks two inner wall bars 13 and the returnbar 15, so that large metal parts and large materials may be discharged.

Free spaces are provided between the inner jacket bars 13 to form slots14 through which material falls when having a diameter which is smallerthan the width of slots 14. The material which falls through the mesh ofscreen drum 2 falls into sand funnel 16a with a discharge opening 16.Larger material is thrown back into the inner chamber of the drum byreturn guide bars as the drum revolves. The material is further crushedby balls 12 and travels slowly toward the discharge chamber 8 due todrum inclination angle A as seen in FIG. 1. While traveling in thedirection 8. the material falls into ring-like screen chambers 4.Consequently. more and more sand is removed, and finally only the largerpieces and the desired metal pieces reach discharge chamber 8.

Material 7 which at the beginning is contaminated with sand is pouredinto hopper 6. It is fed through the hollow shaft 5 and into the drum.

After the material travels as above-described from the drum center indirection B it reaches intermediate annular gap C formed by annularplate 9. Brackets support plate 9 as shown. Gap C is of a size smallenough for preventing balls 12 from passing through. In dischargechamber 8 material 10 falls through annular gap C defined by plate 9 andout through chute II. By combining dust removal chamber 16a with thesand hopper 16, reusable sand may be continuously removed. It is obviousthat efficient separation of sand from the residue is realized. Theinventive apparatus achieves high capacity and continuously dischargesthe sand and residue. Accordingly the invention meets the requirementthat it operate continuously and need not be stopped for emptying theresidue.

In special cases guide pieces 17 or 18 or a combination thereof (shownin outline) may be mounted on the inner casing bars 13 in order toobtain the desired openings or rotational characteristics, or both.

Referring now to FIGS. 5 and 6 a ball mill is shown having the drum in ahorizontal position. Additional sheet metal guide pieces 21 are mountedhelically on the inner casing bars 13 so that material 7 is moved fromhopper 6 in direction C as shown. The material 7 is crushed by balls 12until one part falls through screen 2 into hopper 16. The part whichdoes not fall into the funnel 16, but remains on screen 2, is thrownback into the inner chamber of the drum by means of return guides 15 andis again crushed. Material which cannot be crushed, for example, corepins or metal parts 10 are moved by the guide bars 21 in the directionof C and fall downwardly through recesses 20 into hopper 11. Theopenings 20 are sized so that only residue parts 10 can fall through.Mill balls 12 are too large to pass through apertures 20 and remain inthe drum.

Referring now to FIGS. 3 and 4 there is shown the bearing mount used forsupporting end shaft 22. The mount is used if the material entering theapparatus is at a high temperature.

Bearings 25 disposed on frame 26a and supporting shaft 22 would beplaced on the apparatus of FIGS. 1, 2, 5, and 6. In use, frame 26a wouldreplace frame 26 andassociated bearings of FIGS. 1 and 6 so that a shaftneck 23 of shaft 22 would ride the periphery of roller bearings 25 asseen in FIG. 3. To prevent axial movement of shaft 22 and, consequently,the inventive ball mill, shoulder 23a of shaft 22 thrusts against a sideof bearing 25 as shown. Axial pressure bearing 24 engages the other sideof bearing 25, so that bearing 24 acts as a rotatable thrust support. Asshown the entire bearing apparatus is supported on frame 26a.

While only several embodiments of the present invention have been shownand described, it will be apparent to those persons skilled in the artthat many changes and modifications may be made thereunto withoutdeparting from the spirit and scope of the invention.

I claim:

1. A ball mill for recovering sand from a charge of used casting sandcontaining metallic residue comprisa drum having an interior wall and anexterior wall forming an intermediate chamber therebetween. the exteriorwall including a screen through which sand is screened whilecontinuously leaving said drum as recovered sand;

a plurality of mill balls located within the interior wall of said drum;

feeding means disposed at one end of said drum;

means for longitudinally subdividing the intermediate chamber;

means responsive to the rotation of said drum, for transporting saidcharge toward the end of said drum opposite to said feeding means; and

continuously operating discharge means disposed at said opposite end ofthe drum and provided with openings sized to permit the discharge ofsaid metallic residue while retaining said balls.

2. A ball mill as recited in claim 1 wherein the interior wall comprisesa plurality of elongated inner bars disposed concentric to and about thecentral longitudinal axis of said drum, said plurality of inner barsdisposed so as to define a plurality of slots disposed between adjacentedges of said inner bars for allowing the sand to pass therebetween.

3. A ball mill as recited in claim 3 wherein said means forlongitudinally subdividing comprises a plurality of rings placed withinthe intermediate chamber formed between the interior and exterior wallsand residing on the periphery of said plurality of inner bars, saidrings subdividing the intermediate chamber into a plurality ofintermediate screen chambers allowing the sand to pass therethrough.

4. A ball mill as recited in claim 4 and further comprising a pluralityof helically-disposed guide pieces on the inside surfaces of saidplurality of inner bars and wherein said drum is horizontally mounted sothat as the drum rotates said plurality of helically-disposed guidepieces transport said charge towards said discharge means.

5. A ball mill as recited in claim 5 wherein said feeding meanscomprises a hollow shaft communicating with the interior of said drumand through which the used casting sand is fed.

6. A ball mill as recited in claim 5 wherein said plurality of innerbars is constructed and arranged to provide openings located within saiddischarge means and said openings are sized for passing said metallicresidue while retaining said balls.

7. A ball mill as recited in claim 4 wherein said discharge meanscomprises:

a circular plate included within the interior diameter of said pluralityof inner bars;

a plurality of support brackets placed within said discharge means andsecuring said plate so that the face of said plate is perpendicular toand concentric with the central longitudinal axis of said drum therebydefining an annular gap; and

jacket means disposed about said periphery of brackets and said plate sothat as the metallic residue migrates through the annular gap it dropsinto said jacket means and exits the ball mill.

1. A ball mill for recovering sand from a charge of used casting sandcontaining metallic residue comprising: a drum having an interior walland an exterior wall forming an intermediate chamber therebetween, theexterior wall including a screen through which sand is screened whilecontinuously leaving said drum as recovered sand; a plurality of millballs located within the interior wall of said drum; feeding meansdisposed at one end of said drum; means for longitudinally subdividingthe intermediate chamber; means responsive to the rotation of said drum,for transporting said charge toward the end of said drum opposite tosaid feeding means; and coNtinuously operating discharge means disposedat said opposite end of the drum and provided with openings sized topermit the discharge of said metallic residue while retaining saidballs.
 2. A ball mill as recited in claim 1 wherein the interior wallcomprises a plurality of elongated inner bars disposed concentric to andabout the central longitudinal axis of said drum, said plurality ofinner bars disposed so as to define a plurality of slots disposedbetween adjacent edges of said inner bars for allowing the sand to passtherebetween.
 3. A ball mill as recited in claim 3 wherein said meansfor longitudinally subdividing comprises a plurality of rings placedwithin the intermediate chamber formed between the interior and exteriorwalls and residing on the periphery of said plurality of inner bars,said rings subdividing the intermediate chamber into a plurality ofintermediate screen chambers allowing the sand to pass therethrough. 4.A ball mill as recited in claim 4 and further comprising a plurality ofhelically-disposed guide pieces on the inside surfaces of said pluralityof inner bars and wherein said drum is horizontally mounted so that asthe drum rotates said plurality of helically-disposed guide piecestransport said charge towards said discharge means.
 5. A ball mill asrecited in claim 5 wherein said feeding means comprises a hollow shaftcommunicating with the interior of said drum and through which the usedcasting sand is fed.
 6. A ball mill as recited in claim 5 wherein saidplurality of inner bars is constructed and arranged to provide openingslocated within said discharge means and said openings are sized forpassing said metallic residue while retaining said balls.
 7. A ball millas recited in claim 4 wherein said discharge means comprises: a circularplate included within the interior diameter of said plurality of innerbars; a plurality of support brackets placed within said discharge meansand securing said plate so that the face of said plate is perpendicularto and concentric with the central longitudinal axis of said drumthereby defining an annular gap; and jacket means disposed about saidperiphery of brackets and said plate so that as the metallic residuemigrates through the annular gap it drops into said jacket means andexits the ball mill.